A head-up display (HUD) is an auxiliary apparatus used in vehicles or aircrafts which displays and projects an image presenting dashboard information upon a transparent screen body, such as a windshield, located in front of the observer. The image projected on the screen body will be reflected back to the observer, so that the observer is able to directly read the dashboard information without lowering his head to watch the dashboard. Therefore, the head-up display can avoid interruption of driving attention, thereby increasing driving safety.
In general, a conventional head-up display system includes an image projector, at least one reflecting mirror and at least one lens all installed on the top of the dashboard. The reflecting mirror and the lens are arranged between the image projector and the windshield of the vehicle to change the optical path and concentrate light, in order to correctly and clearly project a virtual image on the windshield.
In the above conventional head-up display system, there is a problem in that the contrast between the virtual image and the background decreases under bright daylight. Since the projector cannot provide virtual images with enough luminous intensity to improve the contrast, the visibility of the virtual image deteriorates.
Besides, the dashboard of a vehicle requires a certain amount of space for installing the above-mentioned conventional head-up display system, which has become a restricting factor for the structure design of the vehicle.
Therefore, in order to solve the problems existing in the conventional technology, as described above, the present disclosure seeks to develop a head-up display system for a vehicle which is able to produce virtual images with high contrast and high intensity of illumination, thereby improving visibility of the display image projected on a front windshield.